Shieldwalls cannot pivot, only wheel, only for 1D6, and only then if the front rank is warriors or elites - all explained on p.37.

Mass formations are not formations so much as groups of groups. So long as you give them the same order and they finish together, each group in the formation can move as it would on its own. The one stipulation Rich has always made is that the groups should not form a column, although that is partly a matter of interpretation, as two groups each in a line ranked one behind the other is OK (it's really a ruling against march columns).